Earth moving scraper bowl construction



Aug. 21, 1962 G. T. COHRON ET AL EARTH MOVING SCRAPER BOWL CONSTRUCTIONFiled May 13, 1960 4 Sheets-Sheet l mwsmozz. GEIZHLD TComeoN Eay E. MnyoATTORNE)? Aug. 21, 1962 a. T. COHRON ET AL 3,049,819

EARTH MOVING SCRAPER BOWL. CONSTRUCTION Filed May 13, 1960 4Sheets-Sheet 2 I l l I l 1 l I I l INVENTORS GEE/4L0 T Cong BYEOY E.Mnya 'ZWJW Au 21, 1962 Gr T. COHRON ETAL 3,049,819

EARTH MOVING SCRAPER BOWL CONSTRUCTION Filed May 13, 1960 4 Sheets-Sheet3 INVENTORS GERRLD T COHRON Roy E. MnYo ATTORNEYS Aug. 21, 1962 G. T.COHRON ETAL 3,049,819

EARTH MOVING SCRAPER BOWL CONSTRUCTION Filed May 13, 1960 4 Sheets-Sheet4 E15 E I E15 .2.. 5 F E- E15 -lE- mmvrons GERALD T COHEON y Roy E. MnyoATTORNEYS 3,049,819 EARTH MQVING SCRAPER BOWL CONSTRUCTION Gerald T.Cohron, East Peoria, and Roy E. Mayo, Peoria,

111., assignors to Caterpillar Tractor Co., Peoria, 111.,

a corporation of California Filed May 13, 1960, Ser. No. 28,872 3Claims. (Cl. 37129) This inventon relates to the construction of thebowls of earth moving scrapers and particularly to improvements in suchbowls through which the power required to load them with earth ismaterially reduced.

The loading of a large scraper bowl of a well-known type involves theraising of mass of earth weighing about 55,000 pounds, a distance of 4feet in approximately 1 minute. According to physical laws, raising ofthis mass to this distance in this period of time requires about 6.7 Hi.It is common practice, however, in loading a tractor drawn scraper ofthis capacity to employ two large track-type pusher tractors to aid inthe loading operation so that a total of 450 usable drawbar HP. isemployed. The horsepower in excess of that actually required to raisethe load is attributable to friction and particularly to the loadingresistance encountered by the soil as it enters the scraper bowl.

It is the object of the present invention to provide a scraper bowl of ashape that materially reduces the resistance to loading which isencountered by soil entering during the loading cycle and which therebyreduces the horsepower required for loading the bowl in most cases toWithin the capacity of a single tractor.

It is a further object of the invention to provide a scraper bowl inwhich the force required for ejecting or discharging the contents of thebowl is greatly reduced.

A still further object of the invention is to provide a bowl for ascraper having side walls which diverge upwardly and outwardlythroughout the major portion of their length but with forward portionscontoured to permit efiicient closing of the open forward end of thebowl by a pivotally mounted apron.

Further objects and advantages of the invention and the manner in whichthe invention is carried into practice are made apparent in thefollowing specification wherein a preferred form of the invention isdescribed in detail by reference to the accompanying drawings.

In the drawings:

FIG. 1 is a view in side elevation of a tractor drawn scraper embodyingthe present invention;

FIG. 2 is a plan view of the scraper unit illustrated in FIG. 1;

FIG. 3 is a front elevation of the scraper shown in FIG. 2 with aportion of the draft frame broken away;

FIG. 4 is a fragmentary View in side elevation illustrating a modifiedform of the invention shown in FIGS 2 and 3;

FIG. 5 is a view in front elevation with portions broken away and shownin section of the scraper shown in FIG. 4;

FIGS. 6 and 7 are schematic views illustrating results of testsproducing soil failure planes under different conditions;

FIGS. 8, 9, 10 and 11 are schematic views representing cross section ofscraper bowls having sides of different configuration and showing thedirection of forces which create resistance to loading of the bowls; and

FIG. 12 is a schematic view of a cutting edge of a scraper bowl inoperation illustrating the manner in which a column of earth passesupwardly into the bowl during filling thereof.

While FIG. 1 of the drawings illustrates a scraper bowl embodying oneform of the present invention, this figure also illustrates the basicparts of a conventional scraper tractor combination which will bedescribed to form a basis for an understanding of the theoriesunderlying the present invention. In this figure a scraper bowlgenerally indicated at 10 is supported at its rear end by wheels 11 andat its forward end by a draft frame generally shown at 12 which ispivoted as at 14 to the sides of the bowl and supported, through aforwardly extending goose neck member 15, by a tractor 16 hereinillustrated as being one of the two-wheel type. An adjustable connectionbetween the draft frame and the bowl which may be a hydraulic cylinderor, as in the case illustrated, a cable 17 leading to power actuatedwinch mechanism on the tractor, not shown, enables raising and loweringof the forward end of the bowl 1% with relation to the ground foradjusting the depth of a cutting edge 18 in the ground while the tractoris pulling the bowl forwardly during a loading cycle. This adjustableconnection is also employed for raising the bowl free of the ground asin the position shown in FIG. 1 for transporting its load. The forwardend of the bowl 19 is closed as by an apron 2.0 the rearwardly extendingsupporting arms 21 of which are pivoted to the sides of the bowl as at22. The apron is moved between its closed position shown and an openposition by power actuated means such for example as hydraulic jacks oneof which is shown at 23 for swinging the apron around the pivotableconnections 22. The rear of the bowl 1% is composed of an ejector 24which is advanceable forwardly through the bowl by means such as ahydraulic j'ack illustrated at 25 so that with the apron 20 in its openposition the contents of the bowl may be ejected forwardly anddischarged over its cutting edge 18.

In the operation of loading a scraper bowl, it is customary to raise theapron to a point where it just clears the ground in advance of thecutting edge 18- which has been lowered into the ground and the soil outupon forward movement of the scraper forms a column which advancesupwardly into the bowl under the influence of substantially verticalforces, this action being schematical ly depicted in FIG. 12 of thedrawings. In FIG. 12 the upwardly moving column is depicted by astippled area to distinguish it from soil already in the bowl.

To observe the effect of friction and other phenomenon tending to opposethe filling of the bowl studies have been made with equipment such asschematically illustrated in FIGS. 6 and 7. In FIG. 6 for example, asmall plate A is buried in a container of soil and lifted as by a rod Bconnected to the plate. An upwardly directed vertical force on the plateA produces shearing stresses of the body of the soil causing failurealong a conical or wedgeshaped surface such as shown at C. The angleformed between the surface of the failure cone and a horizontal planedepends upon the type and condition of the soil but has been found to beapproximately 45 plus /2 where equals the angle of internal soilfriction. The value of has been determined by experiments with a largenumber of various types of soils encountered in earth moving operationsas varying between 15 50.

If the soil on top of the lifting plate A has insufficient internalstrength to maintain the conical form or if there is not enough roomwithin the container for the cone to be established, a wedge of soilwhich may be referred to as dead soil, because it does not have internalmovement during upward movement of the plate, is formed on top of theplate. This may be illustrated by burying a larger plate D in arelatively small container as shown in FIG. 7 and applying upward forcethereto through a rod E. Since the container in this case is not largeenough to permit the formation of a failure cone like that shown in FIG.6, the frictional resistance between the soil and the container sidescause the soil to fail along lines F forming an Patented Aug. 21, I952inverted wedge of dead soil above the plate D. Upon continued upwardmovement of the plate D, the wedge exerts an outward force on theremaining soil in the container, the general direction of which isindicated by arrows in FIG. 7 thus greatly increasing the frictionalresistance to upward movement. In this case, the angle of failure whichdefines the shape of the wedge is again found to be 45 plus 5/2 withrespect to a horizontal plane.

FIG. 8 is a schematic view representing a cross section through aconventional scraper bowl, having the usual vertical side walls, duringthe loading operation wherein a wedge of dead soil corresponding to thewedge of FIG. 7 is being advanced upwardly into the bowl beneath soilalready contained therein creating outward forces in the direction ofthe arrows shown and thus producing tremendous frictional resistance tothe loading of the bowl requiring the extremely high tractive effort andhorsepower Which is exerted during the loading cycle of a conventionalscraper.

FIGS. 9, and 11 of the drawings are schematic views similar to FIG. 8representing three modifications of the present invention which, tovarying degrees, relieve the frictional resistance to the upwardmovement of a column of earth in a scraper bowl. In each of thesemodifications, the side walls of the bowl are flared or inclinedoutwardly, at least in part, to an angle which approaches the angle ofthe soil failure plane represented at C in FIG. 6. While it would bedesirable theoretically to have this angle correspond to the angle C fora particular soil being loaded ,or at least for an average soil whereinthe soil failure plane occurs somewhere between the extreme angles of 52/2 and 70, this angularity has the disadvantage that it either reducesthe capacity of the bowl or increases its overall width.

The optimum angularity of the bowl sides for an average of all soilstested is an angle of approximately from vertical or an included anglebetween the bowl sides of 60. In the interest, however, of maintainingmaximum capacity without unduly increasing the width of the bowl, an 18/z" angle has been selected for the designs represented in FIGS. 9, 10and 11.

In the modification of the invention shown in FIG. 9, the sides of thebowl rise vertically from the bottom of the bowl a distance which is atleast as great as the deepest out which should be made by the cuttingedge, then the major portion of the sides slope outwardly terminating ina short vertical section adjacent their upper edges. With thisconstruction, as indicated by the arrows in FIG. 9, a great portion ofthe frictional resistance to the incoming column of soil is eliminated.

In the modification shown in FIG. 10, the sides slope outwardly from thebottom of the bowl to approximately a half way position and thencontinue vertically upwardly.

FIG. 11 shows the sides of the bowl inclined in an 18 angle throughouttheir entire height producing only very small frictional resistance tothe upward movement of the incoming column of earth.

All of the bowl designs represented by FIGS. 9, 10 and 11 present aproblem in apron design. Ordinarily a scraper apron fits between theinner forward edges of the bowl and since the side walls of the bowl arevertical and parallel as shown in FIG. 8, the apron may be raised alimited distance as for example to the position shown in 'FIG. 12 toprovide an opening above the blade for the admission of earth during theloading cycle. As is apparent from FIGS. 9, 10 and 11, however, an apronfitting 'between the outwardly sloping side walls would, upon beingraised even a short distance be separated from the sloping portions ofthe side walls and permit escape of earth contained by the bowl. Onemethod which suggests itself for correcting this condition is to providean apron which swings in front of rather than between the side walls andof a width equal to the widest part of the bowl. This has thedisadvantage that the apron in its closed position would projectlaterally outwardly a substantial distance from the bottom of the bowlas represented for example by dotted lines showing the outline of suchan apron 20a in FIG. 11.

The manner in which this apron problem is overcome for a bowl with fullsloping walls such as shown in FIG. 11 is illustrated in FIGS. 1, 2 and3 of the drawings wherein the upper forward portions of the bowl sidesare shown as deformed inwardly in a triangular area 26 bringing theirextreme front edges into parallelism. This transformation area isdisposed a considerable distance forwardly of the cutting edge andproduces little if any frictional resistance to the uprising column ofearth dur ing the loading cycle. It also enables the use of an apronwith parallel edges which as most clearly shown in FIG. 4 fits betweenparallel edges throughout the larger portion of its vertical dimensionand overlaps the forward edges of the bowl only at the lower portionthereof so that only the outermost lower corners of the apron extendlaterally beyond the width of the bowl for a very short distance.

Apron construction for the type of bowl shown in FIG. 9 is illustratedin FIGS. 4 and 5 of the drawings wherein the sides of the bowl are alsoshown as inclined inwardly adjacent their forward ends to formtriangular transition areas 28. The lower apex of each of these areascoincides with the upper edge of the lower vertical portions of the bowlshown at 29 in FIGS. 4 and 5 so that the entire forward edge of eachside wall is vertical providing space for the reception of a rectangularapron 20b fitting closely between the side walls throughout its entirerange of movement. In both modifications shown, the arms 21 whichsupport the apron are bent inwardly to conform to the configuration ofthe upper edges of the side walls as most clearly shown in FIG. 2.

With a bowl shaped as indicated in FIG. 10, the forward portion thereofmay be modified in accordance with the teaching of FIGS. 1, 2 and 3 toreceive an apron such as that shown at 20 between its forward edges.

Each of the modifications herein described have the further advantagethat they reduce the force required to eject a load from the scraperbowl. This results from the fact that sticking or jamming of a load asit is pressed forwardly by the ejector is relieved by free upwardmovement permitted by the outwardly sloping side walls.

From the foregoing discussion it is apparent that any angle greater thanformed by the bowl side and the bowl bottom will reduce the forcerequired to load the scraper.

We claim:

1. In an earth moving scraper having a bowl with a bottom, side walls, avertically movable apron forming a front wall, and a cutting edgedisposed forwardly of the bottom whereby the bowl can be loaded byadvancing with the cutting edge in the earth and the apron lowered tothe surface of the earth to induce a column of earth to advance upwardlyinto th bowl, the improvement which includes said side walls beingsloped upwardly and outwardly to reduce frictional resistance to theupward movement of said column and having inwardly and forwardlyconverging forward portions conforming at their forward edges to theparallel edges of said apron whereby the apron may be received betweensaid forward edges as it is raised and lowered.

2. In an earth moving scraper having a bowl with a bottom, side walls, avertically movable apron forming a front wall, and a cutting edgedisposed forwardly of the bottom whereby the bowl can be loaded byadvancing with the cutting edge in the earth and the apron lowered tothe surface of the earth to induce a column of earth to advance upwardlyinto the bowl, the improvement which includes said side walls beingsloped upwardly and outwardly through at least a portion of their heightto reduce frictional resistance to the upward movement of said column,and said sloped portions having inwardly and forwardly convergingforward portions terminating in spaced parallel edges to coincide withparallel edges on said apron.

3. In an earth moving scraper having a bowl with a bottom, side walls, avertically movable apron forming a front wall, and a cutting edgedisposed forwardly of the bottom whereby the bowl can be loaded byadvancing with the cutting edge in the earth and the apron lowered tothe surface of the earth to induce a column of earth to advance upwardlyinto the bowl, the improvement which includes said side walls beingsloped upwardly and outwardly through at least a portion of their heightto reduce frictional resistance to the upward movement of said column,said sloped portions having inwardly and forwardly converging forwardportions terminating in spaced parallel edges to coincide with paralleledges on said apron, said forward portions being disposed forwardly ofsaid cutting edge.

References Cited in the file of this patent UNITED STATES PATENTS WeimerMar. 8, 1938 2,682,120 Wirkkala June 29, 1954 2,795,872 Wardle June 18,1957

